Certain 6H-7,8-dihydrothiapyrano[3,2-d]pyrimidines are disclosed in Belgian Pat. No. 724745 as intermediates for the preparation of compounds with cardiovascular and coronary dilation activity, however, suggestion is made neither of any hypoglycemic activity nor of weight reducing properties for either the intermediates or the final products. Great Britain No. 2119368 discloses 6H-7,8-dihydrothiapyrano[3,2-d]pyrimidines with a very different substitution pattern on the nucleus when compared with the instant compounds. U.S. Pat. Nos. 3,318,883, 3,272,811, and 3,318,881 disclose dihydrothieno[3,2-d]pyrimidines which differ from the instant compounds in having a 5-membered heteroaromatic sulfur-containing ring rather than a saturated 6-membered ring.